Airfield and roadway pavements are deteriorating faster than they are being repaired. In the past, pavements were maintained but not managed, and little regard was given either to life cycle costing or to priority, as compared to other requirements. Letting pavements deteriorate without preventive maintenance is very costly and results in an increased backlog and eventually a loss of assets. As pavement infrastructure has proliferated and aged, a more systematic approach to determining maintenance and rehabilitation (M&R; alternatively: repair) needs and priorities became necessary. Optimum timing of repairs results in improved pavement condition and considerable cost savings over the life of the system. If M&R is performed during the early stages of deterioration, i.e., before the sharp decline in pavement condition, over 50% of lifecycle repair costs are saved. In addition to cost reduction, long periods of closure to traffic and detours can be avoided.
PAVER™ (consisting of a desktop system called MicroPAVER™ and a Web-based system called WebPAVER™) is a successful engineered management system (EMS) for pavements. PAVER™ was developed by the US Army Corps of Engineers Engineering Research and Development Center (ERDC), Construction Engineering Research Laboratory (CERL). PAVER™ aids pavement (M&R) managers in deciding when and where to apply resources for pavement M&R. PAVER™ is used to:                develop and organize pavement inventory;        assess current pavement condition;        develop models to predict future conditions;        document past and estimate future pavement performance;        develop alternatives for M&R based on budget and pavement condition.        
Recent improvements to PAVER™ aid M&R managers in modeling pavement condition and permitting adjustments related directly to budget availability and optimization of available resources down to the project level.
In select embodiments of the present invention, the computer-based Inventory & Work History 101 is based on a prior art hierarchical structure composed of networks, branches, and pavement sections, with user-specified pavement sections being the smallest unit identified for management. This structure allows users to easily organize inventory while providing appropriate fields and levels for storing data. Additional features, such as ‘Copy and Move’, simplify the process of re-defining existing pavement sections and applying work information to multiple pavement sections at once.
Refer to FIGS. 1 and 2. For Condition Assessment 103, select embodiments of the present invention may use the prior art Pavement Condition Index (PCI) 204 as a standard. Further, the American Society for Testing and Materials International (ASTM, Intl.) has adopted the PCI 204 as a standard for assessment of roads (D-6433-03) and airfields (D-5340-04). The PCI 204 is derived using data from inspections and assessments as to the Type 201, Quantity 202 and Severity 203 of “distresses” in a pre-specified basic pavement section, in turn rolled up into assessments of branches and then, finally, to networks of pavements.
As available in the prior art, the PCI 204 provides both a numerical and a “qualitative” estimate 205 (color-coded in one embodiment but not shown in FIG. 2) of pavement condition on a scale from 0 to 100 using terms from “failed” to “good” as qualitative terms representing numerical ranges of the PCI 204. In addition to the PCI 204, select embodiments of the present invention allow pavement M&R managers to use and create other condition indices, including those based on the principles of the PCI 204. Qualitative ranges 205 for the PCI 204 may be customized and used for reporting analysis results in accordance with user requirements. Manuals (existing in the prior art) for roads and airfields show defect type, severity level definitions, and guidelines for the measuring criteria used by inspectors.
Select embodiments of the present invention also employ a prior art interface for importing inspection data from automated collection resources such as those that may be affixed to a vehicle traveling over the target pavement section(s). Select embodiments of the present invention provide users a prior art interface for recording the results of an inspection and an online user's guide for selecting the type of distress and assigning a severity thereto, thereby facilitating the assessment of all pavement distresses on each pavement section, a typical prior art computer page (screen) of which is shown in FIG. 3.
Refer to FIG. 3, a typical screen print available in the prior art for summarizing inspection results as well as providing definitions, including photos 301 of sample pavement distresses (defects). For example, the screen (FIG. 3) of the MicroPAVER™ Users' Guide shows distress (defect) type 303, severity level definitions 305, and guidelines for measuring criteria 306 as well as photo examples 301 typical of the various types of distresses encountered in pavements. The screen also provides areas for inputting requests such as inspection date 302 and description of noted distresses 304. Thus, for pavements, there exists both an interface for accessing the results of an inspection and a guide suitable for explaining and characterizing types of pavement distress and quantifying severity.
From the prior art, a pavement “family” is defined as a group of pavement sections with similar deterioration characteristics. Shahin, M. Y., Pavement Management for Airports, Roads and Parking Lots, 2nd Edition, Springer Science+Business Media, Inc., ISBN 0-387-23464-0, 2005. For example, a user may define a pavement family based on several factors including use, rank, surface type, zone, pavement section category, last construction date (LCD), the PCI, and the like. A user may define as many families as required for accurate condition prediction. Data availability may impose a limitation on the number of discrete families that are defined.
Refer to FIG. 7 showing a typical pavement family deterioration curve 701 from the prior art, plotting the PCI versus Age, with a Critical PCI “range” of 55-70 indicated by the hatched area 702. A Critical PCI is the value of PCI at which the rate of PCI loss “noticeably” increases with time, i.e., the slope of the deterioration curve steepens “suddenly.” Another way of saying this is that the Critical PCI is the value of PCI for which the cost of applying localized preventive maintenance increases at a significantly greater rate at a PCI beyond that PCI. The first point at which the curve 701 begins to rapidly change slope after a moderate aging period is shown at 703. Thus, the point 703 could be considered “the” Critical PCI if one were to use a single value as opposed to a range of values for the Critical PCI. From the prior art, the following procedure is used to formally establish the Critical PCI for a pavement section:                1. develop a family curve for the pavement section under consideration and visually select a first estimate of Critical PCI (either a fixed figure or a range of figures) based solely on the increase in loss rate;        2. select the Localized Preventive M&R Policy to be used in developing Work Plans;        3. apply the selected policy to the pavement sections under consideration;        4. plot the cost (e.g., $/yd2) of Localized Preventive Maintenance per unit area for each of the pavement sections (as shown in FIG. 8 at 804); and        5. select a Critical PCI based on the findings of steps 1 and 4, supplemented with engineering judgment.        
Again refer to FIG. 1. From the prior art, the Condition Analysis & Work Planning framework (feature) 105 allows users to view the condition of an entire network of manmade structure, such as a pavement network, or any specified subset of a network. This feature captures past conditions, including those between inspections that may be based on interpolated values. This feature then enables reporting of projected conditions based on these prediction models. As available from the prior art, outputs from the Condition Analysis and Work Planning framework 105 may be viewed on color-coded 504 Geographic Information System (GIS) maps 501, as shown in FIG. 5 in grey scale, with layer lists 505 that may be selected via user commands 503, some of which are shown for illustration purposes only on the tool bar 502.
As provided in the prior art regarding pavement, M&R types are grouped into four categories, listed in priority order for accomplishing in a timely manner: Localized Safety (Stop-Gap), Localized Preventive, Global Preventive, and Major M&R.
Localized Safety M&R includes the localized distress repair needed to maintain structure, such as pavement, in a safe condition.
Localized Preventive M&R is defined as distress maintenance activities performed with the primary objective of slowing the rate of deterioration. For pavement, these activities include crack sealing, patching and the like.
Global Preventive M&R includes activities applied to a basic managed element, such as an entire pavement section, with the primary objective of slowing the rate of deterioration. For pavement, these M&R activities are primarily for asphalt surfaced pavements, e.g., surface treatments such as fog and slurry seals.
Major M&R includes activities applied to a basic managed element, such as an entire pavement section, to correct or improve existing structural or functional requirements and specifically includes reconstruction and structural overlays. After completing a Major M&R activity, the PCI is re-set to 100.
A prior art Work Plan tool facilitated automated planning, scheduling and budgeting, as well as analysis of alternative pavement M&R activities. A resultant M&R (Work) plan combined basic inventory data with inspection data, maintenance policies, maintenance costs, and predictions of condition, such as may be associated with M&R of pavement. Factors used in determining a user's required M&R include integration of local M&R management practices such as pavement M&R practices.
As shown in FIG. 29, prior art work planning has enabled users to determine how much funding is required to address alternative objectives such as maintaining a current index, such as a PCI, or eliminating backlog. In this example, condition history was documented to establish the PCI v. Fiscal Year (Age) curve 2901. As is apparent, the PCI has fallen from 70 in Year 01 to about 60 in Year 05. Options are considered at Year 05. For this example, the very best condition maintenance is that shown at curve 2902 for which $1.9M/yr is allocated to M&R. As a result of allocating this much to the budget, the M&R backlog is eliminated by Year 09 and the pavement condition improved to a PCI of about 85 in Year 09. The next best condition maintenance alternative, shown in curve 2903, maintains an almost level condition, i.e., maintains the PCI at about 65 until Year 09. This results in a Year 09 PCI that is just slightly better than the “starting” PCI at Year 05. The cost of M&R for this alternative is $800K/yr. The alternative shown at curve 2904 shows the Year 09 PCI just below that at which it began in Year 05. This is achieved by maintaining M&R funding at $500K/yr, the same level as spent in the Year 05. Finally, a “stop gap” alternative is shown at curve 2905. This amount of M&R allows the pavement to degrade at the same rate as before Year 05 by fixing only what requires fixing to safely operate.
As provided in the prior art, results of a manual budget analysis in analyzing a Work Plan output include recommending an M&R category for each basic element, such as a pavement section, for each planning year. Considering economy of scale, it is unlikely that a project will be generated for each basic element. Instead, basic elements, such as pavement sections, are grouped to formulate projects that reduce unit cost and minimize interruption. Also when formulating projects, work is specified in terms of M&R type (e.g., 3-inch overlay for a pavement) rather than by M&R category (e.g., major M&R). Each project may be described by: project name and pavement sections included in the project; M&R types to be performed, assigning each a work date and cost per unit area; altering work items for individual pavement sections, if different from the rest of the sections to be included in a project; and the like.
Based on the concept that it is more economical to maintain pavements above rather than below a critical PCI, a Critical PCI procedure for Work Planning of pavement M&R was developed in the prior art by applying results from a dynamic programming network optimization analysis and life-cycle cost analyses from many projects. As considered in Work Planning, the procedure assigns an appropriate M&R category to individual pavement sections as a function of the PCI of the pavement section and its Critical PCI, prioritizes work, determines budget consequence, establishes budget requirements, and the like.
Disciplined employment of a Critical PCI procedure by users results in maintenance of all pavement sections above the Critical PCI value, thus improving M&R management. By keeping pavement sections above the Critical PCI, emphasis is placed on preventive M&R, i.e. Localized Preventive and Global Preventive M&R. When pavements reach the Critical PCI, they should receive Major M&R. However, in many cases, Major M&R can be performed only as soon as funds are made available.
Refer to FIG. 28, a prior art graphical depiction of the value of localized preventive M&R. As recognized in the prior art, the credit (benefit), ΔT, from applying Localized Preventive M&R can be documented. The application of Localized Preventive M&R is not likely to start until several years, i.e., at x, after the last construction or Major M&R date. That is, it is at the xth year normally when Localized Preventive M&R events, such as crack filling and patching, may be required. To credit the improvement in performance of the pavement section, one has to specify the expected total increase in life, ΔT. The specified increase can be assigned based on the maintenance organization's distress maintenance policy and the type, use, and rank of the pavement section itself. The annual increase in life is calculated by dividing ΔT by the number of years, n, during which the Localized Preventive M&R is applied. As shown for curve 2801, there is no annual increase during the early years when no Localized Preventive M&R is applied but the effect on later years may be significant as shown in curve 2802. This data may be used as input to algorithms used in select embodiments of the present invention for establishing alternative budgets, inspection schedules, M&R Work Plans and the like.
As provided in the prior art for multi-year Work Planning, a pavement section may receive different or repeated M&R events based on condition, rate of deterioration, length of the Period called out in the Work Plan, available budget, and the like. A Work Planning tool may account for a limited budget, i.e., the most realistic scenario. A user may prioritize work based on categories of work, pavement use, relative value of the PCI, and the like. For example, Localized Safety work is given a higher priority than Localized Preventive work while a PCI near the Critical PCI merits a higher priority than a PCI of a higher value. Chapter 10, Shahin (2005). Applying Global Preventive M&R or Localized Preventive M&R is likely to increase the life of the pavement section and increase the PCI. Applying Localized Safety M&R is not likely to increase the life of the pavement section or even stabilize the PCI, thus the common term “stop-gap” is used to describe its effect.
As provided in the prior art, assigning an “appropriate” M&R category is a function of whether a PCI of the pavement section is above or below the Critical PCI. If a PCI is above the Critical PCI, Localized Preventive M&R or Global Preventive M&R may be applied to the individual pavement section. Generally, Major M&R is applied if the pavement section is structurally deficient. Typically, if a PCI is below the Critical PCI, either Localized Safety M&R or Major M&R is applied (many times dependent on funding availability) and no Preventive M&R (Localized or Global) is applied. A more detailed description of the assignment process is presented below with examples of how it is implemented.
Refer to FIG. 9, a graph of cost/unit area versus PCI as presented in the prior art. The straight line curve 902 is an approximation of what is a most likely cost as represented by the dotted curved line 901. Major M&R above Critical PCI has higher priority than Major M&R below Critical PCI in order to minimize expense before the rate of deterioration increases. In select embodiments of the present invention, within each M&R category, a priority factor is assigned based on the combination of pavement use and rank, i.e., a functional classification is assigned. Within each M&R category associated with a priority factor there is likely to be more than one pavement section requiring M&R. In these cases, the PCI may be used to break ties. Priority is determined by three prior art tables that may be edited by the user.
The unit cost of Major M&R above the Critical PCI is much less than that for Major M&R below the Critical PCI. For example, one may perform a 2 to 3-inch overlay on a pavement section that is rated above the critical PCI as compared to a cold mill and overlay done at a PCI below the Critical PCI or a reconstruction done at a very low PCI, e.g., below 30. Typically, Major M&R on a pavement section rated above the Critical PCI is performed when there is a structural deficiency or heavier traffic is expected. Of course, Localized Preventive M&R may be provided as a simple overlay for a pavement section rated at a PCI above the upper part of the Critical PCI range.
Refer to FIG. 10, depicting a prior art procedure for selecting the specific type of Global Preventive M&R 803 for asphalt pavements. Global Preventive M&R 803 is applied based on a specified interval between Global Preventive M&R 803 events. For example, if polished aggregate is present or there is any “bleeding” in low (L), medium (M) or high (H) amounts 1001, an appropriate M&R event may be an aggregate seal or thin overlay 1002. However, if the distress (deficiency) is L, M, or H block cracking; L, M, or H weathering or raveling; or L, M, H cracking 1003, then rejuvenation 1004 may be an appropriate Global M&R event. If neither of the above distress categories 1001, 1003 are present, then an appropriate Global Preventive M&R event ent may be a simple fog seal 1005.
Refer to FIG. 11 for a flow chart describing prior art assignment of M&R categories where PCI≦PCI Critical 1101 as picked off point 1106 on the unit cost/PCI curve 808 of the graph 1102, i.e., a case in which the PCI is “marginal.” The first step is to check on funding availability 1103 based on budget and major M&R priorities. If funding is available, Major M&R is applied and the PCI re-set 1104 to 100. If funds are not available, Localized Safety (stop-gap) M&R is applied 1105, the PCI most likely remains the same, and funding availability is checked in the following planning years. Again, the cost of Localized Safety M&R is determined based on the PCI vs. unit cost relationship curve 808. The unit cost at the current PCI of the individual pavement section is multiplied by the area of the pavement section to estimate current cost.
Refer to FIGS. 1 and 4. From the prior art, the Condition Prediction Modeling function 104 identifies and groups pavements of similar construction that are subjected to similar traffic, weather, and other factors affecting pavement performance. Historical data on pavement condition are used to build “family models” such as the curve 401, with upper and lower bounds 402, that predict future condition of a group of pavements having similar attributes.
Management objectives are achieved when work is performed on time. Costs increase if scheduled Major M&R for an element, such as a pavement section, is delayed. The amount of increase is a function of the PCI 204 at the time major M&R was scheduled (but not done) and the projected rate of deterioration of the pavement section. In the prior art, the penalty for delaying major M&R is calculated by:
      Penalty    ⁢                  ⁢    %    =            (                                    C            f                    -                      C            s                                    C          s                    )        ×    100  where:
Cs=Cost in originally scheduled year, and
Cf=Future Cost=[Mp (1+i)n]+Ld 
where:
Mp=Major M&R cost at the predicted future condition (after n years)
i=Annual inflation rate
n=Time delay (years), and
Ld=Sum of localized stop-gap repair costs over the delay period
The penalty cost is normalized (as above) by dividing it by the original cost (Cs) to determine the relative penalty regardless of the size of a pavement section. Shahin (2005). This facilitates use of the penalty figure for prioritization. An example penalty cost calculation follows.
Year 2005 Major M&R (w/PCI=70); Cs=$40,650
Year 2008 Major M&R (w/PCI=62); Mp=$53,741                i=3%, and        n=3        
Future Cost (Major M&R); Cf=(53,741)(1+0.03)3=$58,724
Localized Safety Cost over the 3-year delay; Ld=$2200
Cf=58,724+2200=$60,924
      Penalty    ⁢                  ⁢    Cost    ⁢                  ⁢    %    =                    (                                            60              ,              924                        -                          40              ,              650                                            40            ,            650                          )            ×      100        ≅          50      ⁢      %      
As can be seen from the prior art, existing methods of “exploring alternatives” are fairly primitive and do not consider the effect of either the completion or delay of current projects on future work and do not allow a user to readily incorporate user-defined projects. Thus a need exists for a better planning methodology.